This invention relates to endless conveyor belt systems, and more particularly, to such systems utilizing metallic belts capable of negotiating edgewise horizontal curves.
In many situations, particularly in the food processing industry, it is desirable to provide a long length of conveyor belt in a relatively small space. For example, such belts find application in the freezing, cooling and heating of foods. In addition, in industries like the baking industry, cakes and other products to be decorated are placed on such belts to permit decorating and other processing steps to be conducted in an assembly line.
A conveyor system for these types of applications is described in U.S. Pat. No. 3,348,659 issued to Roinestad. According to the Roinestad system, the belt is driven and supported by a pair of horizontally spaced apart drums. Support means engage the underside of the belt to support the belt for helical movement upwardly around one of the drums and downwardly around the other of the drums. The helical movement occurs in a plurality of vertically spaced apart loops contiguous to the drums throughout their length, the loops being curved edgewise with the radially inner edge of the belt being in sliding frictional engagement with the drum driving surface. The belt is maintained in tension by engagement with the drum. The frictional engagement between the drum and belt causes the continuous movement of the belt.
Such drive systems suffer from significant disadvantages. For example, the length of the belt is limited because the horsepower required for moving the belt and the tension on the belt are proportional to the length of the belt. About 50 horsepower can be required to pull a belt only 1200 feet, and the high tension on the belt can result in its premature failure. Further, the prior art systems tend to be bulky, requiring large-diameter drums.
A further disadvantage of some prior systems is that only one type of product can be carried on the belt at a time. If products of different weight are carried on the belt, there is a tendency for the belt to tip edgewise with the result that the products slide onto the floor.
In view of these problems, it is apparent that there is a need for a conveyor system utilizing endless belts which permits use of belts of substantially unlimited length, requires low power consumption, is compact, and produces low tension and low wear on the belts.